This invention relates to a bushing assembly/support structure arrangement wherein the bushing assembly is adapted to receive a molten material and includes a plurality of nozzles through which the molten material passes prior to being attenuated into continuous fibers.
In the manufacture of continuous glass fibers, glass forming batch ingredients are added to a melter where they are heated to a molten condition. The molten glass travels from the melter to one or more bushing assemblies by way of a glass delivery system, e.g., a channel and a forehearth. Each bushing has a number of nozzles or tips through which streams of molten glass flow via gravity. Those streams are mechanically drawn to form continuous glass fibers by way of a winder or like device.
A prior art bushing assembly is illustrated in FIG. 1. It comprises a bushing main body 10 having a plurality of side walls 11 (only one of which is illustrated) and a tip plate 12 extending between the side walls 10. The tip plate 12 includes the nozzles 12a through which the streams of molten glass flow via gravity. A first support rail 20 is coupled to a first side wall of the bushing main body 10. A second support rail (not shown) is coupled to a second, opposing side wall of the main body 10. A plurality of C-shaped support brackets 30 (only one of which is illustrated in FIG. 1) are coupled to the first and second support rails 20 and the side walls 11 of the main body 10. Each support bracket 30 comprises outer members 30a and 30b, which are integral with and extend generally orthogonal to a generally horizontal intermediate member 30c. Ends of the outer members 30a and 30b opposite the ends integral with the intermediate member 30c are coupled to a corresponding support rail and main body side wall. A like number of support straps 40 (only one of which is illustrated in FIG. 1) are coupled to and extend from a bushing frame (not shown) and provide upwardly directed forces for supporting the bushing assembly. To insulate the support straps 40 and the bushing frame from electrical and thermal energy flowing through the main body 10, an electrically and thermally non-conductive bar 50 is provided between each support bracket 30 and corresponding support strap 40. Hence, each support strap 40 applies its upwardly directed holding force against a corresponding insulator block/support bracket combination.
It is desirable for all bushing assembly nozzles to be positioned in generally the same horizontal plane. Typically, a plurality of cooling fins (not shown) are provided below the tip plate and extend between rows of the tip plate nozzles. Heat is radiantly and convectively transferred from the nozzles and the glass streams to the fins. If one or more first nozzles are repositioned closer to a corresponding fin, such as due to deformation of the tip plate, the heat transfer rate away from those first nozzles increases. An increase in the heat transfer rate away from a given nozzle results in a decrease in the glass flow rate through that nozzle. A reduction in glass flow rate through a nozzle results in a corresponding fiber being formed having a reduced diameter. Fibers formed having reduced diameters are more likely to break. Breakage of a single fiber during a fiber forming operation results in the operation failing and being shutdown. Consequently, operating costs are increased and productively is decreased.
The bushing assembly illustrated in FIG. 1 is typically formed from an alloy of platinum or a like material and is routinely operated at temperatures exceeding 2200xc2x0 F. At such high operating temperatures and after only a limited amount of time in production, one or more support brackets 30 either deform or separate from a corresponding support rail and main body side wall. Deformation or separation of a support bracket results in a portion of the perimeter of the bushing assembly main body being inadequately supported. This, in turn, can result in a portion of the tip plate being distorted. Tip plate distortion results in one or more nozzles being displaced from a nominal horizontal plane, in which all nozzles are initially positioned. As noted above, nozzle displacement can result in glass flow rate changes. Once a significant glass flow rate change has occurred at one or more nozzles, the bushing assembly must be replaced.
The dimension from the tip plate outer surface to an inner bearing surface on a support bracket intermediate member 30c should be the same for each support bracket. If the support brackets are positioned relative to the tip plate inconsistently, installation of the bushing assembly within the bushing frame/support strap assembly becomes difficult and time consuming. This is because one or more support straps must be reconfigured or machined to compensate for the incorrectly positioned support brackets such that the bushing assembly tip plate is positioned in a generally horizontal plane. Because each support bracket is manually positioned and welded to its corresponding support rail and main body side wall, it is difficult to produce a bushing assembly having support brackets consistently positioned relative to the tip plate.
It is desirable to have a bushing assembly/support structure arrangement where adequate support is provided for a bushing assembly main body over an extended period of time so as to increase the useful life of the bushing assembly. It is also desirable to have a bushing assembly/support structure arrangement where the bushing assembly can be easily installed within a bushing frame/support strap assembly.
With the present invention, an improved bushing assembly/support structure arrangement is provided. The bushing assembly comprises a bushing main body having, in one embodiment, first and second support rails fixedly coupled to opposing sides of the main body. Each support rail has first and second planar surfaces, which define a substantially L-shaped body. The support rails are accurately positioned vis-a-vis an outer surface of a tip plate. A first planar surface of each support rail is then fixedly coupled to a corresponding side wall of the main body. The bushing assembly further comprises a plurality of brackets. Each bracket comprises an intermediate member having a substantially planar face fixedly coupled along substantially its entire length to a corresponding main body side wall. Portions of each support rail extending between first and second leg members of a corresponding bracket function as bearing surfaces for corresponding support straps extending from a bushing frame. Because each support rail is fixedly coupled along substantially its entire length and each bracket is fixedly coupled along substantially the entire length of its intermediate member, each support strap contact region on the first and second support rails is robust and unlikely to distort or sag over extended periods of usage. Accordingly, the time period between bushing assembly changeovers is increased resulting in lower glass fiber production costs.
In accordance with a first aspect of the present invention, a bushing assembly is provided for containing a molten mineral material from which fibers can be attenuated. The bushing assembly comprises a bushing main body comprising at least first and second side walls and a tip plate extending between the side walls. The tip plate contains a plurality of orifices through which molten mineral material flows so as to be attenuated into fibers. The bushing assembly further comprises a first support rail coupled to the main body first side wall and at least one first bracket having an intermediate member coupled to the main body first side wall.
The first support rail may comprise first and second substantially planar surfaces integral with one another and defining an L-shaped body. The support rail first planar surface may be coupled to the main body first side wall. It is also contemplated that the first support rail may be configured so as to define other shapes in cross section, such as, by not limited to, a square, a rectangle, or a triangle.
The bracket may comprise first and second leg members and an intermediate member, with the legs members being located on opposing sides of the intermediate member and extending substantially orthogonal to the intermediate member.
Preferably, the support rail includes first and second slots. The first and second bracket leg members are received in the first and second slots and may be weldably or otherwise coupled to the support rail and the main body first side wall.
The bracket intermediate member is preferably welded to the main body first side wall along substantially the entire length of the intermediate member.
The bushing assembly preferably comprises a plurality of first brackets, each of which includes an intermediate member weldably or otherwise coupled to the main body first side wall. The bushing assembly also preferably comprises a second support rail coupled to the main body second side wall. The second side wall is positioned opposite the first side wall. The bushing assembly also comprises a plurality of second brackets, each including an intermediate member weldably coupled to the main body second side wall.
In accordance with a second aspect of the present invention, a bushing assembly/support structure arrangement is provided. The arrangement comprises a bushing assembly and a support structure. The bushing assembly includes a bushing main body comprising at least first and second side walls and a tip plate extending between the side walls. The tip plate contains a plurality of orifices through which molten mineral material flows prior to being attenuated into fibers. The bushing assembly further comprises a first support rail coupled to the main body first side wall, and at least one first bracket having an intermediate member coupled to the main body first side wall. The support structure comprises a bushing frame, and at least one first support strap. The support strap has a first end fixedly coupled to the bushing frame and second end extending toward a first location on the support rail adjacent the first bracket for supporting the bushing assembly.
The arrangement further comprises an insulating member located between the support rail first location and the support strap second end. The support strap second end applies a weight-bearing support force against the support rail first location via the insulating member.
The first support rail may comprise first and second substantially planar surfaces integral with one another and defining an L-shaped body. The support rail first planar surface is preferably coupled to the main body first side wall.
The bracket may comprise first and second leg members. The legs members are located on opposing sides of the intermediate member and extend substantially orthogonal to the intermediate member.
The first location on the support rail is located between the first and second legs of the first bracket.
The support rail includes first and second slots. The first and second leg members are received in the first and second slots and weldably or otherwise fixedly coupled to the support rail and the main body first side wall.
The bracket intermediate member is welded to the main body first side wall along substantially the entire length of the intermediate member.
The bushing assembly preferably comprises a plurality of first brackets, each including an intermediate member weldably coupled to the main body first side wall. The support structure preferably comprises a plurality of first support straps, each including a first end fixedly coupled to the bushing frame and a second end extending toward a corresponding location on the support rail for supporting the bushing assembly.
The bushing assembly further comprises a second support rail coupled to the main body second side wall, and a plurality of second brackets, each including an intermediate member weldably coupled to the main body second side wall.